Soft Decision Error Assisted Layered Multiuser Detectors for MIMO 2D Spread MC DS-CDMAs

In this paper, we present two layered multiuser detectors (MUDs) for MIMO frequency-time-domain (FT-domain) spread multi-carrier (MC) direct sequence code division multiple access (DS-CDMA) systems. We assume the users are organized into groups, and each user is assigned a unique Time-domain (T-domain) signature code. Moreover, the same group´´s users share a unique F-domain signature code. However, as CDMA-like systems, the MC DS-CDMA system is still affected by multiple access interference (MAI). To mitigate MAI, we propose two layered MUDs that exploit layered soft decision errors. Specifically, in a trade-off between the performance and the computational complexity, only the soft decision errors of one user/one group are used in the proposed layered MUDs. Simulation results demonstrate that the proposed layered MUDs outperform existing approaches and the computational complexity is modest.